Get object property name from value

Question

Let's say that I have a JavaScript object like this:

var obj = {
    a: 1, 
    b: 2, 
    c: 3,
    d: 4
};

How do I get the property c of the object for example knowing the value 3?

The only solution I see is to iterate through the object and find the key — Arun P Johny
– Arun P Johny, Commented Nov 20, 2013 at 3:57

Arun P Johny · Accepted Answer · 2013-11-20 03:58:47Z

1

There is no built-in method to do this, but you can easily write one

var obj = {
    a: 1,
    b: 2,
    c: 3,
    d: 4
};
var key;
for (var x in obj) {
    if (obj.hasOwnProperty(x) && obj[x] == 3) {
        key = x;
        break;
    }
}
console.log(key)

Demo: Fiddle

answered Nov 20, 2013 at 3:58

Arun P Johny

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2 Comments

Rajaprabhu Aravindasamy Over a year ago

obj.hasOwnProperty(x) what's the need of doing this check.? x inside that for must be a key from that object obj right?

Arun P Johny Over a year ago

it is to handle if it has prototypical inherited properties

passer · Accepted Answer · 2013-11-20 04:03:15Z

1

try something like iterating the object?

for(var property in obj) 
{
  if(obj.hasOwnProperty(property) ) 
  {
    if(obj[property] === value)
      return property;
  }
}

answered Nov 20, 2013 at 4:03

passer

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